🌴 Macadamia

What it looks like

How to grow

Macadamia is an evergreen tree from the rainforests of southeast Queensland, grown for smooth-shelled nuts (Macadamia integrifolia) and its rougher-shelled cousin M. tetraphylla. Garden trees reach 30–50 feet tall with a dense, broad crown, so plant a grafted tree of a named cultivar — ‘Beaumont’, ‘Kau’, or ‘Keaau’ are common choices — rather than a seedling, which may take a decade to crop and may crop poorly. Site in a sheltered spot: macadamias are brittle in strong wind, and young trees are frost-tender.

Plant in deep, rich, well-drained soil with plenty of organic matter. Macadamias flower in winter and spring in hanging clusters, pollinated largely by bees; planting two different cultivars improves set. Prune lightly to remove dead wood and keep the canopy open — heavy pruning costs you a season of nuts.

USDA zones

Macadamias grow outdoors in zones 9–11 (some sources extend to 12), with mature trees tolerating only light, brief frosts around 30°F and young trees needing protection from any frost. In Florida, south and central Florida are the plausible outdoor range; north Florida gardeners should plan on frost protection or a large container moved under cover. Anywhere colder, grow it as a container tree in a greenhouse.

Water & feeding

Water regularly — young trees need ample water, and steady moisture suits macadamias better than long dry spells, especially during flowering and nut fill. Mulch heavily to hold moisture and protect shallow roots. Feed lightly and often with a balanced fertilizer low in phosphorus (macadamias, like other Proteaceae, are sensitive to excess phosphorus); compost or worm castings are a safe, gentle base feed. Avoid heavy nitrogen, which pushes leafy growth over nuts.

Common problems

• Frost damage — blackened leaves and dead twigs after a cold night. Protect young trees with frost cloth and site away from cold-air hollows.
• Phytophthora root rot — in poorly drained soil. Plant on high ground with drainage, never in a soggy spot.
• Wind breakage — brittle branches snap in storms. Plant in a sheltered position and stake young trees.

Harvest

Nuts mature over a long season: husks turn brown and split, and nuts drop to the ground — gather them regularly rather than letting them sit in damp leaf litter. Husk, then dry nuts thoroughly in a warm, airy spot for several weeks before cracking; properly dried kernels store for months. One household note: macadamia nuts are toxic to dogs, so keep fallen nuts and bowls of kernels away from pets.

Saving seeds

Macadamia seed will grow a tree. It will not reliably grow the macadamia you ate, and the wait is long enough that the distinction matters.

A seedling macadamia takes seven to ten years or more to bear, and the nuts it makes are variable — thicker shells, smaller kernels, or a blander flavor than its parent. Named cultivars like Beaumont, 344, and A4 do not come true from seed, full stop. If you want a particular nut, grafting is the only sure route, and grafted trees are what the guide’s harvest timing is based on. A grafted tree can bear in four to five years. A seedling makes you wait twice as long for a nut you did not order.

Seed is genuinely good for two things: rootstock to graft onto, and the experiment. If you want to try it, use a fresh nut from a tree you like, crack the shell carefully, and sow the kernel promptly in a deep pot of moist, free-draining mix. Macadamia seed does not store well; it dries out and dies, so do not save it for a project next month. The seed makes a taproot early, so a deep pot matters more than a wide one. Keep it warm and evenly moist, and be patient. Germination usually comes in a few weeks.

Isolation barely matters for seed you plan to use as rootstock, since any seedling grafts fine. It matters more if you are chasing a seedling that resembles its parent, because bees cross-pollinate macadamias freely and a seedling’s father could be any macadamia in the neighborhood. In practice, most home growers have one tree, and one tree’s seed is what it is.

Florida honesty: macadamia is a South Florida tree, and a frost-sensitive one. A hard freeze will finish a young tree, so grow it in a sheltered spot or in a pot you can protect. In Central Florida it is a sheltered-spot gamble, and in North Florida it is a container plant. Graft in spring, when the tree is growing strongly, and protect the young tree from its first winter.

Varieties

Every named variety of Macadamia with its own growing guide:

• Beaumont Macadamia — The vigorous, heavy-bearing macadamia: buttery nuts on a handsome evergreen that hates frost and loves a long, warm season.
• Kau Macadamia — The Hawaiian orchard macadamia: high-quality, smooth-shelled nuts on a tree bred for production, not just beauty.